Wanda Kuhl

Sodium-potassium-ATPase activity is influenced by ethnic origin and not by obesity.

Previous investigations have suggested that red-cell ouabain binding (an indirect measure of sodium-potassium-ATPase activity) is lower in severely obese patients than in normal controls. We now confirm that ouabain binding measures sodium-potassium-ATPase activity, and we demonstrate that the level of this activity is genetically determined. The activity of this enzyme differs in various ethnic and racial groups, relatively high levels being encountered in non-Jewish white subjects, particularly those with some Scandinavian ancestry. On the other hand, black, Asian, and Jewish white subjects have lower sodium-potassium-ATPase activity. In contrast, no difference was found in red-cell sodium-potassium-ATPase activity between severely obese and normal persons, nor could we confirm a putative effect of food intake on the level of the red-cell enzyme. We suggest that in most earlier studies in which differences were found between normal and severely obese persons, those differences could have been due to differences in the ethnic origins of the obese and control populations.

Galactokinase Deficiency as a Cause of Cataracts

Abstract Galactokinase and galactose-1-phosphate uridyl transferase assays were carried out on blood samples from 210 persons in whom cataracts developed before the age of 40. In two patients, both...

Mutation analysis of glucose-6-phosphate dehydrogenase (G6PD) variants in Costa Rica

SummaryGlucose-6-phosphate dehydrogenase (G6PD) deficiency has previously been reported among both the black and white populations of Costa Rica. All 28 G6PD A — samples were found to be of the common G6PD A-376G/202Atype. A previously described mutation associated with nonspherocytic hemolytic anemia, G6PD Puerto Limón, was found to be due to a G→A transition at nucleotide (nt) 1192, causing a glu→lys substitution. Mutations in this region of the G6PD molecule seem invariably to be associated with chronic hemolytic anemia. G6PD Santamaria had been described previously in two unrelated white subjects. We found that both did, indeed, have the same mutations. In this variant the A→G substitution at nt 376 that is characteristic of G6PD A was present, but an A→T mutation at nt 542, apparently superimposed on the ancient G6PD A mutation, resulted in an asp→val substitution. Thus, the gain of a negative charge at amino acid 126 was counterbalanced by the loss of a charge at amino acid 181, giving rise to a variant with the G6PD A mutation but with normal electrophoretic mobility.

Glucose-6-phosphate dehydrogenase variants in Hawaii.

Sequence analysis has been performed on the DNA of 13 glucose-6-phosphate dehydrogenase (G6PD) deficient males from Hawaii, 6 of Filipino, 6 of Laotian, and 1 of Chinese extraction. Four different mutations were found: A-->T at cDNA nt 835, G-->A at nt 871, C-->T at nt 1360, and G-->A at nt 1388. The mutations at nt 835 and nt 1360 have not been described previously, and the latter, in particular, appears to be relatively common. The nt 1360 mutation changes the same codon as is altered in a previously described mutation, G6PD Andalus.

Some Mexican glucose-6-phosphate dehydrogenase variants revisited

SummaryGlucose-6-phosphate dehydrogenase (G6PD) deficiency appears to be fairly common in Mexico. We have now examined the DNA of three previously reported electrophoretically fast Mexican G6PD variants, — G6PD Distrito Federal, G6PD Tepic, and G6PD Castilla. All three of these variants, believed on the basis of biochemical characterization and population origin to be unique, have the G→A transition at nucleotide 202 and the A→G transition at nucleotide 376, mutations that we now recognize to be characteristic of G6PD A —. Two other Mexican males with G6PD deficiency were found to have the same mutation. All five have the (NlaIII/ FokI/PvuII/PstI) haplotype characteristic of G6PD A in Africa. Since the PvuII+ genotype seems to be rare in Europe, we conclude that all of these G6PD A-genes had their ancient origin in Africa, although in many of the Mexican patients with G6PD A −202A/376G the gene may have been imported more recently from Spain, where this variant, formerly known as G6PD Betica, is also prevalent.

Linkage between a PvuII restriction fragment length polymorphism and G6PD A-202A/376G: evidence for a single origin of the common G6PD A — mutation

SummaryDNA samples from 29 males with the G6PD A-phenotype and 14 males with a G6PD B phenotype were studied for the presence of each of four polymorphic restriction sites in the glucose-6-phosphate dehydrogenase locus. All G6PD A-subjects with the G6PD A-202A/376G genotype, regardless of population origin, shared identical haplotypes. In view of the fact that at least one of the restriction sites, the PvuII site in the intron between exon 5 and 6, has thus far been uncommon in the populations studied, it seems likely that the G6PD A-mutation at nucleotide 202 arose relatively recently and in a single individual.

Prenatal diagnosis of glucose-6-phosphate-dehydrogenase deficiency.

Prior to the development of the DNA-based technology reliable prenatal diagnosis of G6PD deficiency was not possible. We show that, using PCR amplification and restriction endonuclease digestion, prenatal diagnosis is possible. We have now been able to determine that the male fetus of a mother heterozygous for G6PD Mediterranean had inherited the maternal X chromosome with the normal G6PD gene.

Blood cell phosphogluconolactonase: assay and properties.

Summary. 6‐Phosphogluconolactonase (6‐PGL) catalyses the second reaction of the hexosemonophosphate pathway. Although the ‐Iactone of 6‐phosphogluconic acid is the natural substrate for this enzyme, the more stable γ‐lactone may also be used. We prepared the γ‐lactone of 6‐phosphogluconic acid from 6‐phosphogluconate. When stored in dimethylsulfoxide, this material was found to be stable in liquid nitrogen for several months. A method for measuring 6‐phosphogluconolactonase (6‐PGL) using the γ‐lactone as substrate has been developed, after defining conditions under which spontaneous hydrolysis of the lactone is relatively slow and the enzymatic velocity is relatively rapid.

The Molecular Biology of Gaucher Disease

Several decades of investigation of Gaucher disease by conventional biochemical techniques has greatly increased our understanding of this disorder. Its cause is a deficiency of the lysosomal enzyme glucocerebrosidase leading to the accumulation of glucocerebroside in the tissues. However, our understanding of some aspects of Gaucher disease remains incomplete. For example, its presentation may vary from a neuronopathic disorder with a fatal outcome in the first year of life to a benign storage disorder first diagnosed in old age, and the causes of the marked differences in clinical severity have eluded us. Moreover, efforts to devise a treatment strategy have not been successful.